<a href="http://www.phrasebank.manchester.ac.uk/introductions.htm" target="_blank">Academic Phrasebank</a>

This web site above is run by The University of Manchester and primary for writers who publish research papers. However, there are some useful expressions included. For example, let's check out this link below.

<a href="http://www.phrasebank.manchester.ac.uk/classifying.htm" target="_blank">http://www.phrasebank.manchester.ac.uk/classifying.htm</a>;

These approaches are good to use in Task 1 questions and precise examples.

Here is for Task 2.

<a href="http://www.phrasebank.manchester.ac.uk/causes.htm" target="_blank">http://www.phrasebank.manchester.ac.uk/causes.htm</a>;

You'll see some structures possible to be used in the task 2 essay. There are more helpful formurations to explore.

Please feel free to make a comment and good luck for your study.